Designating targets using laser spots is a widely known technique due to the high precision of the pointing laser device and the relatively low cost of the homing head that utilizes a sensor which receives the energy reflected from the illuminated target, and then processing it for generating steering commands for homing the intercepting platform (such as an intercepting missile) towards the target (such as a moving vehicle).
In accordance with known laser spot guiding techniques (as illustrated schematically in FIG. 1), a laser designator 1 fitted on a given platform 2 constantly tracks the target 3 and illuminates it in a laser beam 4 pulsed spot. Also shown is an intercepting missile 5 employing a sensitive sensor. The sensor's surface is usually divided into four equal sectors (not shown in FIG. 1) and associated spectral filter which transfers most of the energy (reflected from the illuminated target as well as a certain (low) portion of noise that stems, e.g. from sunlight (not shown)). The energy received in each of the sectors of the sensor is converted into corresponding signal intensity. The differences between the signal intensities in the respective sectors are used to calculate the direction to the target (line of sight—LOS 6) and/or the change of direction LOS rate. The calculated LOS and/or LOS rate serve for steering the missile for homing onto the target 7.
In accordance with a typical (yet not exclusive) scenario, the laser designator 1 transmits pulses at a rate of 10-20 Hz, facilitating sampling at this rate for homing purposes. The wavelength that is used is e.g. 1064 nanometers. Each pulse is narrow (15-20 nanoseconds) and has generally an energy of 60 to 120 m joule. The energy received by the sensor is converted to electrical current/voltage, depending also on the sensor's sensitivity. In order to secure sufficient Signal/Noise ratio (e.g. above 6) that will be received in the sensor and will allow to discern between the true signal from the ambient noise (such as sunlight) at a sufficient level of certainty, the output power of the laser designator 1 is of the order of 3-8 Megawatts. This output power of the laser would allow the intercepting missile to process the so discerned signal at sufficient range from the target, affording at least 6-10 time constants which are required for properly steering of the intercepting missile in order to achieve an accurate homing 7 onto the target. In case the energy received at the sensor is too low, this will hinder properly. discerning between the signal and noise, thereby adversely affecting the calculation of the angular error and angular error rate, and thereby degrading the prospects of duly hitting the target.
The hitherto known techniques suffer from one or more of the following limitations, including:                The relatively high price tag of the laser designator (which illuminates the target) that meets the specified operational specification,        The relatively large physical dimensions of the laser designator as well as the relatively high weight which hinders the possibility to carry portable laser designators by a person such as an infantry individual, or fitting them in, a vehicle, such as small flying platforms (for instance UAV) which can fly under the clouds.        
There is, thus, a need in the art for a new low-weight and low-cost laser designator device, and a corresponding sensor and associated processor that will facilitate appropriate designating of moving targets, e.g. for display purposes, and whose laser can be carried by a platform that is limited by its, capacity to carry heavy payload, such as an infantry soldier, low weight flying platform (possibly) unmanned air vehicle (UAV), etc.
There is still a need in the art for laser designators and/or sensor and an associated processor that will facilitate the operation of intercepting platforms such as missiles for homing onto moving or stationary targets.
There are known in the art low pulse power lasers, for instance those utilizing fiber optics technology (hereinafter fiber optics lasers). A typical, yet not exclusive example is the 10-20W Pulsed Fiber Lasers commercially available from SPI Lasers Company, which is illustrated schematically in FIG. 2. Such lasers are in many cases considerably lighter and cheaper than the specified laser designators, but they have low pulse power capacity of the order of 1-4 mjoules per pulse. The fiber optic lasers can generate a relatively high pulse frequency of the order of 5000 Hz at very accurate timing.
As shown in FIG. 2, a typical, yet not exclusive, fiber laser designator 20 consists of a power supply 21 coupled to a trigger laser diode 22 and pumping laser diode 23 both coupled to fiber laser amplifier 24 which, in turn, is coupled to beam spot focusing telescope 25 that generates the laser spot that illuminates the target. Note that the generated laser pulses are rather narrow, say of the order of 20-25 nanoseconds.
The operation of the fiber optics laser designator is generally known per se and therefore will not be further expounded upon herein.
There is a further need in the art for utilizing the low weight and relatively cheap fiber optics lasers for the specified applications such as designating targets (e.g. for display purposes), and/or homing an intercepting object, such as a missile, onto a mobile or stationary target, and/or measuring distance and/or velocity to targets. These applications are applicable, notwithstanding the inherent low pulse power output of the fiber optics lasers.
List of related art: WO 2005/050240 entitled “Method and System for Determining the Range and Velocity of a Moving Object” discloses a device for determining the range of a moving object, the device including at least one sampler, a multi-process array coupled with the sampler and a selector coupled with the multi-process array, the sampler producing a plurality of sampled signals by sampling a received signal respective of a sequence of pulses transmitted toward the moving object, the multi-process array running a plurality of processes, each of the processes associated with a respective time shift which is determined according to a respective radial velocity assumption of the moving object with respect to the device and with a pulse rate of the sequence of pulses, each of the processes producing a signal summation by sequentially shifting the sampled signal by the respective time shift and adding together the sampled signals, the selector determining the range according to at least one signal summation which includes a summed pulse event.